Dissimilar friction stir welding of immiscible titanium and magnesium

Dissimilar friction stir welding of an immiscible metal combination, titanium and magnesium, was performed. Aluminum thin foil was inserted between the titanium and magnesium in order to simultaneously react with these two immiscible materials. The welding parameters including aluminum foil thickness, probe offset and welding speed were optimized to fabricate a sound titanium/magnesium joint. The influence of welding conditions on the reaction layer formation, aluminum distribution and tensile strength of the obtained joints was systematically examined. With an increase in the aluminum foil thickness, the size and amount of the welding defects generated inside the magnesium stir zone increased due to the poor material flow. The optimal joint showed the highest tensile strength of similar to 150 MPa, which is similar to 88% of the tensile strength of pure magnesium, and fractured at the magnesium heat affected zone, which is attributed to the formation of properly thin intermetallic compound layer at the weld interface and the inhibition of brittle intermetallic compounds formation inside the magnesium stir zone.